摘要:

The effect of spacers on the binding of atrazine-tagged liposomes to anti-atrazine antibodies was studied. Atrazine derivatives with alkyl spacers of different length (C4, C6, C8 and C12) were synthezised and conjugated to dipalmitoyl phosphatidyl ethanolamine. The conjugates were incorporated into liposomal membranes of DPPC/DPPG/cholesterol containing ascorbic acid as entrapped marker. Tagged liposomes were bound to a monoclonal anti-atrazine antibody immobilized on a nitrocellulose membrane, destroyed by the addition of surfactant and the marker was detected electrochemically using printed thick-film electrodes. Our results show that liposomes incorporating a hapten with short alkyl spacer binds better to the immobilized antibody. These results will allow optimization of liposomes as an enhancement system in electrochemical or optical biosensors.

ISSN:0003-2719    

DOI:10.1080/00032719608002267

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

An amperometric immunoassay technique utilizing a highly dispersed immunoelectrode was developed. The assay method is based on the ‘sandwich’ scheme of immunointeraction. Rabbit IgG has been used as model analyte. Horseradish peroxidase labelled conjugates were employed coupled with amperometric detection of iodine reduction. Highly dispersed ULTI carbon serves as an immunosorbent and at the same time as an electrode material. It was found that the dependence of immunoelectrode response on the time of incubation during the second stage of ‘sandwich’ -based assay was complex. This is probably due to non-equilibrium immuno-agglomeration of sub-micron sized particles of immunosorbent. The improvement in the sensitivity of immunoelectrode by increasing the amount of immunosorbent was demonstrated. The increase in the magnitude of the immunoelectrode response is proportional to the increase of the amount of immunosorbent. A detection limit of 10 pM has been achieved with an overall assay time of less than 20 minutes.

ISSN:0003-2719    

DOI:10.1080/00032719608002268

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A new polymer (polyhistidine) modified electrode has been fabricated and was applied to the catalytic oxidation of ascorbic acid (AA), reducing the overpotential by 400 mV. The catalytic rate constant of the modified electrode for the oxidation of AA was determined using a rotating electrode. The catalytic current was linearly dependent on the ascorbic acid concentration between 5×10−5and 2×10−3M. The catalytic effect on the AA resulted in the separation of the overlapping voltammograms of AA and dopamine (DA) in a mixture. This allowed the determination of AA in the presence of DA. The electrode was rather stable even after several months; a reproducible response of AA was obtained.

ISSN:0003-2719    

DOI:10.1080/00032719608002269

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Two variants of partial least-squares methodology (PLS-1 and PLS-2) have been used for the analysis of ternary and quaternary mixtures of acetaminophen-acetylsalicylic acid-codeine and caffeine, respectively. This methodology permits the simultaneous quantification of the aforementioned drugs even with closely overlapping spectral bands without any separation step. The concentration ranges are 4.0–12.0, 0.2–1.0 and 4.0–12.0 μg·ml−1for acetaminophen-acetylsalicylic acid-codeine and 10.0–20.0, 6.0–16.0, 1.0–5.0 and 0.2–1.0 μg·ml−1for acetaminophen-acetylsalicylic acid-caffeine and codeine, respectively. A systematic study of the experimental data by applying an exhaustive statistical analysis to demostrate the validity of the proposed methods is presented. The results of the determination of these drugs in pharmaceutical preparations are also presented. The analytical results were quite good in all cases.

ISSN:0003-2719    

DOI:10.1080/00032719608002270

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A spectrophotometric-indirect procedure for the determination of metamizol is described. The method is based on the reaction of the drug in a solid-phase (lead dioxide immobilized in a polyester resin bed) in acidic media (perchloric acid 0.01 M as carrier). The lead dioxide reactor provides simultaneously an effective oxidation of the drug and a controlled liberation of Pb(II) which acts as catalyst on the reaction pyrogallol red-potassium persulphate; the oxidation of the red pyrogallol results in a less coloured solution. The decreased red colour (negative FIA peaks) is monitored at 520 nm. The calibration graph is linear in the interval 2–16 ppm in metamizol. The relative standard deviation for the determination of 10.4 ppm of metamizol is 2.9% (n=23) and the sample throughput is 72 h−1.

ISSN:0003-2719    

DOI:10.1080/00032719608002271

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A direct and simple first derivative spectrophotometric method has been developed for the determination of mefenamic acid and paracetamol in pharmaceutical formulations. A methanolic hydrochloric acid solution was used as solvent for extracting the drugs from the formulations and subsequently the samples were evaluated directly by derivative spectrophotometry. Simultaneous determination of both drugs can be carried out using the zero-crossing and the graphical methods. The methods do not require simultaneous equations to be solved. The calibration graphs were linear in the ranges from 1.8 × 10−6to 1.6 × 10−4M of mefenamic acid and from 4.1×10−6to 1.4 × 10−4M of paracetamol. The ingredients commonly found in commercial pharmaceutical formulations do not interfere. The proposed method was applied to the determination of these drugs in tablets.

ISSN:0003-2719    

DOI:10.1080/00032719608002272

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The voltammetric behaviour of minocycline at a water/nitrobenzene interface has been studied by normal, semi-differential and semi-integral cyclic voltammetry. The semi-differential cyclic voltammetry can be used as a rapid, simple method for determination of the antibiotic minocycline in the range of 5–200 ug/ml and the relative standard deviation is within 3%. Drug samples were analyzed and satisfactory results were found as compared with US Pharmacopoeia method.

ISSN:0003-2719    

DOI:10.1080/00032719608002273

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Arsenic (III), arsenic (V), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were separated by ion-exchange chromatography. The elution sequence was as follows: 1.5 M ammonia followed by 0.12 M hydrochloric acid yielding As(III) 1 M hydrochloric acid followed by water yielding first As(V) and then MMA. Detection was by hydride generation-atomic absorption spectrometry. No interference was noted from 13 metallic ions.

ISSN:0003-2719    

DOI:10.1080/00032719608002274

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A simple and rapid atomic absorption method for the determination of some amino acids containing a sulphur group is described. The studied compounds are cysteine, cystine and methionine. The method is based on the addition of an excess of mercury (II) chloride in phosphate buffer, pH 9, forming a white precipitate; the unreacted mercury is separated by centrifugation and the mercury ions in both precipitate and filtrate are determined by atomic absorption spectrophotometry at 253.6 nm. The concentration of the studied amino acids is then indirectly determined from a calibration curve for standard mercury (II) chloride solution.

ISSN:0003-2719    

DOI:10.1080/00032719608002275

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The solution fluorescence properties of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were compared with the solid-matrix luminescence properties of PhIP. The fluorescence properties were obtained in ethanol and several binary solutions of ethanol:water. An ethanol solution of PhIP gave a very strong fluorescence signal and the ethanol:water solutions only showed a small increase in the fluorescence signal. Acidic solutions of PhIP in ethanol:water (7:3) showed a major decrease in fluorescence intensity with at HCl of 10−4M and greater, but NaOH solutions of PhIP did not affect the fluorescence intensity to any great extent. Both acidic and basic solutions gave fluorescence emission spectra that were shifted to longer wavelengths. Solid-matrix room-temperature fluorescence (SMRTF) and solid-matrix room-temperature phosphorescence (SMRTP) were readily obtained on filter paper. SMRTP showed some distinct advantages over SMRTF and gave a limit of detection of 0.2 ng on filter paper. Several aspects of both solution luminescence and solid-matrix luminescence of PhIP are discussed.

ISSN:0003-2719    

DOI:10.1080/00032719608002276

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor